Did US troops go back home after World War 1 or did some stay until World War 2?

They returned home. Between end of WW1 (1918) and the start of WW2(1939), there were 21+ years. Most of the soldiers left the army. This resulted in a reduced size of army that may the US unprepared for the start of WW2.

Most of the units returned home and were deactivated. There were some units in the Pacific area at the start of WW2 but I don't think these units were there in 1918. When the US started preparing for WW2, the National Guard units were activated and sent into training. A great deal of units left home, but one or two was left as as 'collaterall', The units there received replacements, and took many combat trainings, preparing for a war. Many of the units are still there.